Mounted assemblies for aircraft, wheels and tires

ABSTRACT

The invention relates to mounted assemblies for aircraft and to the wheels and tires which constitute them. The mounted assemblies for aircraft to which the invention relates are characterized in particular by the combination of an inflation pressure greater than 9 bar and a relative deflection of the tire greater than 30%, the wheel comprising a rim for receiving the tire and more specifically seats receiving the beads of said tire. According to the invention, the rim comprises a drop-centre functionality and is advantageously of monobloc type.

The invention relates to mounted assemblies for aircraft and to thewheels and tires which constitute them. The mounted assemblies foraircraft to which the invention relates are characterized in particularby the combination of an inflation pressure greater than 9 bar and arelative deflection of the tire greater than 30%.

The deflection of a tire is defined by the radial deformation of thetire, or variation in the radial height, when it changes from anon-loaded state to a statically loaded state, under rated load andpressure conditions.

It is expressed in the form of a relative deflection, defined by theratio of this variation in the radial height of the tire to half thedifference between the external diameter of the tire and the maximumdiameter of the rim measured on the hook. The external diameter of thetire is measured statically in a non-loaded state at the rated pressure.

The reinforcement armature or reinforcement of tires and in particularof aircraft tires is currently—and most frequently—formed by a ply or astack of several plies conventionally referred to as “carcass plies”,“crown plies”, etc. This manner of designating the reinforcementarmatures derives from the manufacturing process, which consists ofproducing a series of semi-finished products in the form of plies,provided with cord reinforcing threads which are frequentlylongitudinal, which are subsequently assembled or stacked in order tobuild a tire blank. The plies are produced flat, with large dimensions,and are subsequently cut according to the dimensions of a given product.The plies are also assembled, in a first phase, substantially flat. Theblank thus produced is then shaped to adopt the toroidal profile typicalof tires. The semi-finished products referred to as “finishing” productsare then applied to the blank, so as to obtain a product ready to bevulcanized.

Such a type of “conventional” process involves, in particular for thephase of manufacture of the blank of the tire, the use of an anchoringelement (generally a bead wire), used for anchoring or holding thecarcass reinforcement in the zone of the beads of the tire. Thus, inthis type of process, a portion of each of the plies constituting thecarcass reinforcement (or only a part thereof) is turned up around abead wire arranged in the tire bead. In this manner, the carcassreinforcement is anchored in the bead.

The fact that this conventional type of process has become morewidespread in the industry, despite numerous variants in the manner ofproducing the plies and assemblies, has led the person skilled in theart to use a vocabulary modeled on the process; hence the generallyaccepted terminology, comprising in particular the terms “plies”,“carcass”, “bead wire”, “shaping” to designate the change from a flatprofile to a toroidal profile, etc.

There are nowadays tires which do not, properly speaking, comprise“plies” or “bead wires” in accordance with the preceding definitions.For example, document EP 0 582 196 describes tires manufactured withoutthe aid of semi-finished products in the form of plies. For example, thereinforcement elements of the different reinforcement structures areapplied directly to the adjacent layers of rubber mixes, the whole beingapplied in successive layers to a toroidal core the form of which makesit possible to obtain directly a profile similar to the final profile ofthe tire being manufactured. Thus, in this case, we no longer find“semi-finished products”, nor “plies”, nor “bead wires”. The baseproducts, such as the rubber mixes and the reinforcement elements in theform of cords or filaments, are applied directly to the core. As thiscore is of toroidal form, the blank no longer has to be shaped in orderto change from a flat profile to a profile in the form of a torus.

Furthermore, the tires described in this document do not have the“conventional” upturn of the carcass ply around a bead wire. This typeof anchoring is replaced by an arrangement in which circumferentialcords are arranged adjacent to said sidewall reinforcement structure,the whole being connected by an anchoring or bonding rubber mix.

There are also processes for assembly on a toroidal core usingsemi-finished products, such as strips, specially adapted for quick,effective and simple laying on a central core. Finally, it is alsopossible to use a mixture comprising at the same time certainsemi-finished products to produce certain architectural aspects (such asplies, bead wires, etc.), whereas others are produced from the directapplication of mixes and/or reinforcement elements.

In the present document, in order to take into account recenttechnological developments both in the field of manufacture and in thedesign of products, the conventional terms such as “plies”, “beadwires”, etc., are advantageously replaced by neutral terms or termswhich are independent of the type of process used. Thus, the term“carcass-type reinforcing thread” or “sidewall reinforcing thread” isvalid as a designation for the reinforcement elements of a carcass plyin the conventional process, and the corresponding reinforcementelements, generally applied at the level of the sidewalls, of a tireproduced in accordance with a process without semi-finished products.The term “anchoring zone”, for its part, may equally well designate the“traditional” upturn of a carcass ply around a bead wire of aconventional process and the assembly formed by the circumferentialreinforcement elements, the rubber mix and the adjacent sidewallreinforcement portions of a bottom zone produced with a process usingapplication on a toroidal core.

Hereafter, “axial” is understood to mean a direction parallel to theaxis of rotation of the tire; this direction may be “axially inner” whenit is directed towards the inside of the tire and “axially outer” whenit is directed towards the outside of the tire.

“Radial” is understood to mean a direction perpendicular to the axis ofrotation of the tire and passing through this axis of rotation. Thisdirection may be “radially inner” or “radially outer” depending onwhether it is directed towards the axis of rotation or towards theoutside of the tire.

“A radially oriented reinforcement element” is understood to mean areinforcement element contained substantially within one and the sameaxial plane.

“A circumferentially oriented reinforcement element” is understood tomean a reinforcement element oriented substantially parallel to thecircumferential direction of the tire, that is to say forming with thisdirection an angle which does not diverge by more than five degrees fromthe circumferential direction.

“Reinforcement element” is understood to mean equally well monofilamentsand multifilaments, or assemblies such as cables, plied yarns oralternatively any equivalent type of assembly, whatever the material andthe treatment of these reinforcement elements, for example surfacetreatment or coating or pre-sizing in order to promote adhesion to therubber.

“Contact” between a reinforcement element and an anchoring rubber mix isunderstood to mean the fact that at least part of the outercircumference of the reinforcement element is in intimate contact withthe anchoring rubber mix; if a reinforcement element comprises acovering or a coating, the term “contact” means that it is the outercircumference of this covering or coating which is in intimate contactwith the anchoring rubber mix

“Elasticity modulus” of a rubber mix is understood to mean a secantmodulus of extension at 10% deformation and at ambient temperature; themeasurement is effected after a first accommodation cycle up to 10%deformation:${- E_{10}} = {{\frac{F_{10}}{S \times ɛ_{10}}\quad{i.e.\quad E_{10}}} = {{\frac{F_{10}\left( {1 + ɛ_{10}} \right)}{S_{0} \times ɛ_{10}}\quad{and}\quad E_{10}} = \frac{F_{10} \times 1.1}{S_{0} \times 0.1}}}$in which ε₁₀ is equal to 0.1; with E₁₀: secant modulus of extension at10% deformation; F₁₀: tensional force at 10% extension; S₀: initialsection of the test piece; S: section of the test piece at thedeformation of extension ε; in the case of rubber material, it is knownthat: ${S = \frac{S_{0}}{1 + ɛ}};$and ε₁₀: deformation of extension at 10%. The measurements of elasticitymodulus of a rubber mix are carried out under tension in accordance withStandard AFNOR-NFT-46002 of September 1988: the nominal secant modulus(or apparent stress, in MPa) at 10% elongation is measured in a secondelongation (i.e. after an accommodation cycle) (normal conditions oftemperature and relative humidity in accordance with StandardAFNOR-NFT-40101 of December 1979).

“Tg” of an elastomer is understood to mean the glass transitiontemperature thereof measured by differential thermal analysis.

“Static creep test” is understood to mean a test in which test piecesare prepared, the useful part of which has a length of 70 mm, a width of5 mm and a thickness of 2.5 mm (these test pieces are cut fromvulcanized sheets of a thickness of 2.5 mm); the test pieces are placedin an oven at 150° C. and a 3 kg weight is immediately hung from them;the test is thus carried out with an initial stress of:$\sigma_{0} = {\frac{Mg}{S_{0}} = {2.35\quad{MPa}}}$with M: weight applied, g: gravity acceleration and S₀: initial sectionof the test piece being measured; the elongation of the useful part ofthe test piece is measured as a function of time; the “amount of staticcreep” corresponds to the variation of deformation over a given time,for example between 3 and 5 hours' testing:$\tau = \frac{\Delta\quad ɛ}{\Delta\quad t}$where: Δε=ε(t₂)−ε(t₁) variation in the deformation measured duringΔt=t₂−t₁ in minutes (min).

“Rheometry test” is understood to mean an alternating shearing test at adeformation of ±0.2 degrees, a frequency of 100 cycles/min, atemperature of 197° C. and a duration of 10 min; rheometer fromMonsanto; the test is performed on a disc of uncured mix, the changeover the 10 min. in the torque resulting from the shearing imposedbetween the two faces of the disc is recorded; the change in the torqueafter the maximum measured will be particularly noted here: if thetorque measured remains stable, there is no reversion, that is to say,reduction in the stiffness of the test piece; if the torque measureddecreases, it indicates that there is reversion; the phenomenon ofreversion results in a reduction in the rigidity of the test piece underthe test conditions; it is a test of the thermal stability of the mix athigh temperature; $r = {\frac{C_{\max} - C_{10}}{C_{\max}} \times 100}$is the amount of reversion at the end of the test; C_(max) is themaximum torque measured and C₁₀ is the torque measured after 10 minutes'testing.

As far as the cords or metal cables are concerned, the measurements ofbreaking load (maximum load in N), tensile strength (in MPa) andelongation at break (total elongation in %) are carried out undertension in accordance with Standard ISO 6892 of 1984.

As far as the cords or textile cables are concerned, the mechanicalproperties are measured on fibers which have been subjected to priorconditioning. “Prior conditioning” is understood to mean storage of thefibers for at least 24 hours, before measurement, in a standardatmosphere in accordance with European Standard DIN EN 20139(temperature of 20±2° C.; relative humidity of 65±2%). The mechanicalproperties in extension (tenacity, modulus, elongation and energy atbreak) are measured in known manner using a ZWICK GmbH & Co (Germany)1435-type or 1445-type tension machine. The fibers, after receiving aslight prior protective twist (helix angle of approximately 6°), aresubjected to traction over an initial length of 400 mm at a nominalspeed of 200 mm/min. All the results are an average of 10 measurements.

The tires may, as previously mentioned, have different types ofconstruction.

U.S. Pat. No. 4,832,102 for example describes an aircraft tirecomprising a crown, two sidewalls and two beads, a carcass reinforcementand a crown reinforcement in which the carcass reinforcement comprisestwo circumferential alignments of reinforcing threads of high elasticitymodulus, anchored in the two beads, and the crown reinforcementcomprises at least one working block with at least one ply ofreinforcing threads of high elasticity modulus. The carcassreinforcement is anchored in the beads by turning up, around a beadwire, the two circumferential alignments of first reinforcing threads ofhigh elasticity modulus.

Patent WO 02/00456 describes a different type of aircraft tires thecarcass reinforcement of which comprises two or three circumferentialalignments of reinforcement elements of high elasticity modulus andanchoring means of said reinforcement elements, constituting the carcassreinforcement, within each bead. The anchoring means in accordance withthis document are formed of circumferentially oriented cords axiallybordering the circumferential alignments of the reinforcement elementsof the carcass reinforcement, said reinforcement elements of the carcassreinforcement and the circumferentially oriented cords being separatedby a bonding rubber mix of very high elasticity modulus. The use ofcords makes it possible to obtain satisfactory rigidity with a bulk ofthe bead which is reduced as much as possible; the compactness of thebead is of paramount importance for aircraft tires to reduce theconsequences of heating of said beads.

Aircraft tires must withstand extreme conditions during service, inparticular in terms of applied load and speed, taking into account theirlow weight and size. As a result, despite their very high inflationpressures, greater than 9 bar, their loading or deflection duringoperation may commonly reach values double those observed forheavy-vehicle tires or passenger-car tires.

During takeoff, very high speeds, of the order of 350 km/hour or even450 km/hour, are achieved, and hence the heating conditions are alsovery harsh.

All these conditions are particularly disadvantageous for the enduranceof the beads of these tires.

These conditions are also restricting with regard to the holding of thetires on the rim. They have hitherto resulted in tires comprising anextremely rigid bottom zone or bead zone which permits good holding onsaid rim. This rigidity of the bottom zone of the tire consequentlynecessitates rims made in several parts which permit mounting anddemounting of the aircraft tires.

Furthermore, the mounted assemblies thus produced for aircraft requirestrict, rigorous and frequent examination. These inspections may beaccompanied by demounting of the mounted assembly and dissociation ofthe wheel and of the tire. These technical operations are longwinded andrequire action by a highly-qualified workforce.

The particular aim of the invention is a mounted assembly or tire-wheelassembly for aircraft which facilitates these technical inspections andmore particularly which facilitates demounting and remounting of themounted assemblies during the life of an aircraft tire.

This object has been achieved according to one aspect of the inventionby a mounted assembly for aircraft formed of a wheel and a tirecomprising in particular beads, the inflation pressure of which isgreater than 9 bar and the relative deflection of which is greater than30%, said wheel comprising a rim for receiving the tire and morespecifically seats receiving the beads of said tire, said rim comprisinga drop-centre functionality.

According to one preferred embodiment of the invention, the rim is ofmonobloc type.

A drop-centre functionality is to be understood to mean that the wheelcomprises a structure which imparts a functionality comparable to thatof a drop centre of a conventional monobloc rim for applications otherthan those of aircraft; the function of a drop centre is in particularto permit mounting of a tire in combination with a certain deformationof the beads thereof. This mounting method is entirely conventional inapplications other than those of aircraft. In these other applications,it is conventional, for mounting a tire on a monobloc wheel, to provide,in the part located between the seats of the wheel, an indented zone ordrop centre which makes it possible to receive in succession part ofeach of the beads of the tire in order to mount it.

The beads of the tire of the mounted assembly according to the inventionare advantageously ovalisable, that is to say deformable in their plane,preferably under industrially acceptable forces.

More preferably still, the beads of the tire of the mounted assemblyaccording to the invention may be warped, that is to say their perimeteris deformable in the axial direction.

The Applicant noted that it was possible, by influencing certaincriteria, also to produce mounted assemblies for aircraft the tires ofwhich lend themselves to being mounted on a rim comprising a drop-centrefunctionality.

There was thus unexpectedly obtained a mounted assembly for aircraftconsisting of a tire and a wheel and more specifically of a rimcomprising a drop-centre functionality advantageously of monobloc type,without sacrificing in particular the endurance of the tire and theclamping of said tire on the rim. This realization is in particularsurprising if it is recalled that the technology of mounting tires onmonobloc rims, which has been conventional in all categories of landvehicles for many years, has never applied to the field of aircraft,despite the considerable expansion of this mode of transport.

The mounting and demounting of the mounted assemblies according to theinvention can thus be effected more simply and more quickly than for awheel consisting of several parts, because the tools and the skillsrequired for these operations are simpler than in the mounting anddemounting operations conventionally practiced. This of course haseconomic advantages of different orders as far as the direct means ofimplementing and the workforce and its necessary training are concerned.

Furthermore, the possibility of mounting an aircraft tire on a wheel ofmonobloc type may make it possible to constitute a mounted assemblyaccording to the invention the weight of which is substantially lessthan the weight of a conventional mounted assembly the wheel of which isformed of several parts. This may also result in substantial economicadvantages, as the saving in weight of the mounted assembly may resultin an increase in the transportable weight or in a reduction in the fuelconsumption of the aeroplane.

The conventional process for mounting a tubeless tire on a monobloc rimcomprising a drop centre for applications other than aircraftapplications consists of different stages which are as follows: first ofall, part of the first bead is passed over the rim flange and this partis placed in the drop centre. The rest of the bead can then be passedover the flange by slightly ovalising the corresponding bead of thetire. The same applies for passing the second bead over the flange ofthe rim. The mounting is then terminated by a final stage of inflationto a pressure such that it ensures that the beads are put in place onthe seats bearing on the rim flanges. During this last stage, the beadsmay cross humps which form an obstacle to the passage of said beads asfar as their respective seat and then prevent the risks of unseating.

The invention provides for this drop-centre functionality to be able tobe fulfilled for example by a limited indented zone on the periphery ofthe wheel or alternatively by one or more limited openings on theperiphery of the wheel. In this latter case of embodiment, the inventionadvantageously provides for the braking system to be integrated in thewheel, coming to block said opening(s). This blocking of the opening(s)may make it possible to function as an anti-unseating device, becausethe blocking of the opening(s) eliminates the drop-centre functionalitynecessary for demounting of the tire or for the unseating thereof. Sucha system may therefore possibly make it not necessary to have humps.

In the same manner, the invention provides for the openings providingthe drop-centre functionality possibly to be blocked by any means knownto the person skilled in the art once they have fulfilled their functionduring mounting of the tire.

The invention also provides for the means providing the drop-centrefunctionality to possibly constitute part of the braking device which isintegrated inside the wheel.

According to one advantageous embodiment of the invention, the seats ofthe rim of the wheel of the mounted assembly have a slope of 5°.

According to another embodiment of the invention, the seats of the rimof the wheel of the mounted assembly have a slope greater than 5° andpreferably less than 15°.

According to the latter embodiments of the invention, according to whichthe seats of the rim have a slope, the endurance of the beads of thetire can be improved.

A first variant embodiment of the invention advantageously providesthat, the tire comprising a crown, two sidewalls and two beads, acarcass reinforcement anchored in the two beads and a crownreinforcement, in which the carcass reinforcement comprises at least onecircumferential alignment of reinforcement elements and in which theanchoring means of said reinforcement elements within each bead compriseat least one circumferentially oriented reinforcement element, thecarcass reinforcement of the tire comprises at least one layer ofreinforcement elements having a zone of upturn around at least onecircumferentially oriented reinforcement element.

According to this first variant embodiment of the invention, the mountedassembly comprises an aircraft tire in which the carcass reinforcementis anchored in the beads by turning up around at least onecircumferentially oriented reinforcement element, such as a bead wire.

A second variant embodiment of the invention advantageously providesthat, the tire comprising a crown, two sidewalls and two beads, acarcass reinforcement anchored in the two beads and a crownreinforcement, in which the carcass reinforcement comprises at least onecircumferential alignment of reinforcement elements and in which theanchoring means of said reinforcement elements within each bead compriseat least one circumferentially oriented reinforcement element, the meansfor anchoring said reinforcement elements within each bead of the tirecomprise circumferentially oriented reinforcement elements axiallybordering said circumferential alignments of said reinforcement elementsof the carcass reinforcement.

The invention also proposes an aircraft wheel comprising a rim forreceiving a tire, comprising in particular beads, and more specificallyseats receiving the beads of said tire, the inflation pressure of themounted assembly formed of the wheel and said tire being greater than 9bar and the relative deflection of which is greater than 30%, said rimcomprising a drop-centre functionality.

Preferably, the rim of the wheel according to the invention is ofmonobloc type.

As previously mentioned, according to a first embodiment of theinvention, the seats of the rim of the wheel have a slope of 5°.

According to another embodiment of the invention, the seats of the rimof the wheel have a slope greater than 5° and preferably less than 15°.

The invention also proposes an aircraft tire, the inflation pressure ofwhich is greater than 9 bar and the relative deflection of which isgreater than 30%, comprising a crown, two sidewalls and two beads, acarcass reinforcement anchored in the two beads and a crownreinforcement, in which the carcass reinforcement comprises at leastone, and preferably at least two, circumferential alignments ofreinforcement elements and in which the means for anchoring saidreinforcement elements within each bead comprise at least onecircumferentially oriented reinforcement element, the beads of the tirebeing ovalisable, that is to say deformable in their plane, preferablyunder industrially acceptable forces.

More preferably still, the beads of the tire may be warped, that is tosay the perimeter of which is deformable in the axial direction.

The invention proposes another aircraft tire, the inflation pressure ofwhich is greater than 9 bar and the relative deflection of which isgreater than 30%, comprising a crown, two sidewalls and two beads, acarcass reinforcement anchored in the two beads and a crownreinforcement, in which the carcass reinforcement comprises at leastone, and preferably at least two, circumferential alignments ofreinforcement elements and in which the means for anchoring saidreinforcement elements within each bead comprise at least onecircumferentially oriented reinforcement element, and at least oneanchoring rubber mix in contact with the circumferential reinforcingthread and the reinforcement elements of the carcass reinforcement, therubber mix having an elasticity modulus, at a deformation of 10%, ofless than 20 MPa.

The tire thus defined according to the invention has beads, the rigidityof which, which is less than that of conventionally-manufacturedaircraft tires, makes it possible to facilitate the mounting anddemounting of said aircraft tire. Surprisingly, the Applicant has notedthat this anchoring rubber mix made it possible, in spite of itsrigidity, which is very much less than what was advocated previously, toretain very satisfactory properties, in particular endurance properties,of the beads in question.

According to a preferred variant embodiment, the anchoring rubber mixcomprises at least one synthetic elastomer included in the group of“SBRs”, or butadiene/styrene copolymers, and “BRs”, or polybutadienes,with a total proportion of synthetic elastomer greater than 50% of thetotal weight of elastomers.

Preferably, the total proportion of synthetic elastomer is of between 55and 65% of the total weight of elastomers.

Above 65%, the tack of the connecting rubbers becomes insufficient andthis causes problems in building the beads of the tires; on the otherhand, below 55%, the resistance of the anchoring rubber mixes to staticcreep stress at high temperature deteriorates.

The anchoring rubber mix preferably comprises an SBR of a Tg of between−70° and −25° C. with a proportion by weight greater than 20% of thetotal weight of elastomers.

It may also comprise a BR of a Tg of between −110° and −90° C. with aproportion by weight of less than 40% of the total weight of elastomers.

In fact, the presence of BR improves the thermal stability of theanchoring rubber mix at high temperature; however, beyond 40% of thetotal weight of elastomers, the anchoring rubber mix becomes difficultto produce.

According to one advantageous embodiment, the anchoring rubber mixwithstands without breaking a static creep stress at 150° C. under aninitial stress of 2.35 MPa for at least 5 hours.

Preferably, the anchoring rubber mix has an amount of static creep at150° C. under an initial stress of 2.35 MPa of less than 2×10⁻³/min forbetween 3 and 5 hours' applied stress.

Preferably, said anchoring rubber mix has an amount of reversion after10 min at 197° C. of less than 10% and preferably less than 5%.

According to a first embodiment of the invention, this applies to anaircraft tire in which the carcass reinforcement of the tire comprisesat least one layer of reinforcement elements having a zone of upturnaround at least one circumferentially oriented reinforcement element,such as a bead wire.

According to this first embodiment, it appeared that the rubber mixaccording to the invention makes it possible to impart, as describedpreviously, a certain flexibility to the bead which facilitates themounting and demounting of the tire.

More advantageously still, according to this first embodiment, when thecarcass reinforcement is turned up around a bead wire, the rubber mix isadvantageously present, apart from the zone between the bead wire andthe carcass reinforcement, within the bead wire, between the differentreinforcement elements constituting it. For certain types of tire,provision may advantageously also be made to subdivide the bead wire(s)to increase the proportion of rubber mix according to the inventionrelative to the proportion of reinforcement element in a given zone.This may result in the presence of numerous subdivisions of bead wires,whether arranged in organized manner or not. The bead wire(s) may beformed of cords or cables selected from the group of carbon, tungsten,aramid, glass-fiber or steel reinforcing threads.

According to a second embodiment of the invention, the invention appliesto an aircraft tire in which the carcass reinforcement is anchored inthe beads by means of circumferentially oriented reinforcement elementsaxially bordering said reinforcement elements of the carcassreinforcement.

According to this second embodiment, in which the anchoring of thecarcass reinforcement and the circumferential reinforcement elements isobtained by an anchoring rubber mix, it appeared that said rubber mixaccording to the invention provides sufficient flexibility to improvethe conditions of mounting and demounting aircraft tires on/from theirwheels.

In accordance with this second embodiment, the invention advantageouslyprovides for the circumferential reinforcement elements to be cables.

Preferably, said cables have a penetrability of between 80 and 100%, thebreaking load of said cables being greater than 150 daN and said cableshaving an elongation at break greater than 4%.

Using cables makes it possible to improve and facilitate the manufactureof the tires according to the invention using manufacturing technologiesof the type on a toroidal core. The Applicant has observed that the factof replacing, in the tire according to the invention, anchoring of thecarcass reinforcement by means of circumferential cords coupled with thereinforcement elements of the carcass reinforcement by means of ananchoring rubber mix with anchoring by means of cables as definedpreviously makes it possible to improve the yield of the manufacturingprocess. Furthermore, it would appear that the use of the cables definedaccording to the invention makes it possible to retain compactness ofthe beads of the tire for satisfactory rigidity for the applications inquestion.

In fact, it would appear that selecting cables having a penetrabilitysuch as described permits hooking in the uncured state of the cables inthe zone of the bead satisfactorily without any risk of having saidcables become detached, even partially, during the stages of manufactureof the later tire which are carried out before curing said tire.

Furthermore, using cables as circumferential reinforcement elements inaccordance with this second embodiment of the invention makes itpossible to warp the beads of the tire or to deform the perimeter in theaxial direction. Such deformation promotes the mounting and demountingof an aircraft tire according to the invention still further. Suchdeformation furthermore makes it possible, under very simple conditions,to mount and demount tires on/from monobloc rims, that is to say in asingle part.

Using a bead wire, in accordance with the first embodiment of theinvention, formed of cords or cables, associated with a rubber mixaccording to the invention present in the zone between the bead wire andthe carcass reinforcement and/or within the bead wire, between thedifferent reinforcement elements which constitute it, also permitsmounting and demounting of tires on/from monobloc rims. Such operationshowever necessitate greater forces than in the case previously mentionedin accordance with the second embodiment of the invention.

The penetrability according to the invention is the ability of therubber to penetrate the free zones of a cable, that is to say the zoneswhich do not comprise material; it is expressed as a percentage of saidfree zones occupied by rubber after curing and determined by an airpermeability test.

This air permeability test makes it possible to measure a relative indexof air permeability. It is a simple way of indirectly measuring thedegree of penetration of the cable by a rubber composition. It isperformed on cables extracted directly, by decortication, from thevulcanized rubber plies which they reinforce, and which therefore havebeen penetrated by the cured rubber.

The test is carried out on a given length of cable (for example 2 cm) asfollows: air is sent to the entry of the cable, at a given pressure (forexample 1 bar), and the quantity of air at the exit is measured, using aflow meter; during the measurement, the sample of cable is locked in aseal such that only the quantity of air passing through the cable fromone end to the other, along its longitudinal axis, is taken into accountby the measurement. The flow rate measured is lower, the higher theamount of penetration of the cable by the rubber.

The values of elongation at break according to the invention permitoptimization of the effectiveness of working of the cables, because inthe techniques of manufacture on a toroidal core, the cables are woundcircumferentially to form several radially concentric or helicoidalturns permitting better anchoring between the cables and thereinforcement elements of the carcass reinforcement. The values ofelongation at break of the cables according to the invention permitdeformation of said cables which results in a greater effectivenessyield of said turns. In other words, the deformation of said cablesaccording to the invention makes it possible to obtain a morehomogeneous distribution, according to the winding length, of thestresses withstood by one and the same winding of such a cable whichdoes not have said elongation characteristics.

Consequently, the combination of the elongation at break of the cablesand their breaking load according to the invention makes it possible toretain a compactness of the bead which is satisfactory for the intendedapplications.

According to a preferred embodiment of the invention, the breaking loadof the cables is less than 400 daN. A breaking load greater than such avalue may result, in particular in the case of an overall value ofbreaking load of the fixed bead and of an imposed cable diameter, in areduction in the number of turns of said cables and hence in a reductionin the anchoring height between the reinforcement elements of thecarcass structure and the circumferentially oriented cables. Such areduction in the anchoring height may be detrimental to the quality ofsaid anchoring. Furthermore, if the increase in the breaking load of thecables is combined with an increase in the diameter of said cables, thismay create problems of bulking in particular in terms of widening thebottom zone.

More preferably still, the elongation at break of the cables is lessthan 8%. A greater elongation might result in tires having a rigidity ofthe beads, for high pressures, which is not sufficient to guarantee theholding of said tire on a rim and to guarantee the transmission of thebraking torques.

The values of elongation at break of the cables according to theinvention are advantageously obtained by heat treatments of the cableswhich are referred to as “high-elongation” treatments. Such treatmentsknown to the person skilled in the art are described for example inEuropean Patent EP 0 751 015.

According to one advantageous embodiment of the invention, the cablesaccording to the invention comprise a conventional adherent coating suchas a brass coating so as to improve the adhesion between said cables andthe rubber mixes.

The circumferentially oriented cables preferably have a modulus ofextension greater than that of the reinforcement elements of the carcassreinforcement. They are preferably selected from the group consisting ofcarbon, tungsten, aramid, glass-fiber or steel reinforcing threads.

According to another characteristic of the tire according to theinvention, considering ΣR_(I) as being the total of the rigidities ofextension of the circumferentially oriented cables arranged axiallyinternally relative to the carcass reinforcement, and considering ΣR_(E)as being the total of the rigidities of extension of thecircumferentially oriented cables arranged axially on either side of thecarcass reinforcement, then:$0.6 \leq \frac{\sum R_{I}}{\sum R_{E}} \leq 1.5$and preferably: $0.7 \leq \frac{\sum R_{I}}{\sum R_{E}} \leq 1.3$

Keeping within these limits for the ratio between the total rigidity ofextension of the circumferentially oriented cables arranged inside thecarcass reinforcement in each bead and the total rigidity of extensionof the circumferentially oriented cables arranged to the outside of thecarcass reinforcement has the advantage of making the stress applied onthe cables oriented circumferentially in the bead more homogeneous,whatever their position.

According to a preferred embodiment of the invention, the outer surfaceof the bead of the tire according to the invention comprising a seatfollowed by a frustoconical wall of substantially radial orientationadjacent radially internally to a wall of cross-section substantially inthe form of an arc of a circle and of centre C arranged externallyrelative to the bead, these walls being intended to bear against thehook and the flange of a suitable rim, considering a line CD, passingthrough the bead of the tire, forming an angle α=+45±5 degrees relativeto the axis A of the tire, all of the circumferentially oriented cablesare arranged at a radial distance from the axis of the tire less than orequal to this line CD. This line CD defines substantially an embeddingzone which is very rigid, in which the deformations are very muchreduced, and a zone of flexure radially above CD. The fact that all thecircumferentially oriented cables are in the embedding zone reinforcesthe endurance of the bead.

Preferably, the bead of the tire according to the invention having anouter surface intended to come into contact with the correspondingsurface of the seat and of the hook of the rim, after mounting on saidrim and inflation of the tire, the contact zone between the outersurface of the bead and the rim extends at least as far as point B ofthe hook of maximum radius R_(J).

Advantageously, Φ being the diameter of the circumference of the outersurface of the bead intended to come to bear against the circumferenceof the hook of the rim of maximum radius R_(J), then:Φ=2(R _(J)−ε)with ε being between 0.5 and 2 mm.

This enables the bead to be “seated” properly on the seat and the hookof the rim and has the advantage of limiting the curvature of thecircumferential alignments of the carcass reinforcement during travel,particularly in the contact area.

According to the invention, the reinforcement elements constituting thecarcass reinforcement may be any type of reinforcement elements in cordform, capable of reinforcing a given matrix, for example a rubbermatrix. As reinforcement elements, mention will be made, for example, ofmultifilament yarns, these yarns possibly being twisted on themselves ornot, of unit threads such as cylindrical or oblong single cords, with orwithout a twist on themselves, cabled yarns or plied yarns (“cords”)obtained by cabling or plying operations on these unit threads or theseyarns, such reinforcement elements possibly being hybrid ones, that isto say, composite ones, comprising elements of different natures.

“Plied yarn” (or “folded yarn”) is understood to mean a reinforcementelement formed of two single yarns or more assembled together by plyingoperations; these single yarns, which are generally formed ofmultifilament yarns, are first of all plied individually in onedirection (S or Z direction of twist) during a first plying stage, thentwisted together in the opposite direction (Z or S direction of twist,respectively) during a second plying stage.

According to one advantageous embodiment of the invention, thereinforcement elements constituting the carcass reinforcement are, forexample, made of aromatic polyamide or reinforcement elements such asthose described in patent application WO 02/085646. These may be cordsor cables.

More advantageously still, the carcass reinforcement of the tiresaccording to the invention comprises two or three circumferentialalignments of reinforcement elements for example.

Advantageously, more specifically as far as the tires produced on a hardcore are concerned, each circumferential alignment of the carcassreinforcement, within each bead, is bordered axially internally andaxially externally by circumferentially oriented cables.

According to one advantageous embodiment, relating even morespecifically to tires produced on a hard core, the reinforcementelements of the carcass reinforcement form forward and return pathsarranged adjacently, with, at the level of each bead, loops connectingone forward path to one return path each time.

In variant embodiments of the invention, the crown reinforcement of theaircraft tire according to the invention preferably comprises at leastone working block with one or more layers of reinforcement elementswhich are parallel to in each layer, oriented substantiallycircumferentially; these are advantageously reinforcement elements madeof aromatic polyamide, or reinforcement elements such as those describedin patent application WO 02/085646.

If necessary, the crown reinforcement comprising a central zone and twolateral zones, the working block furthermore comprises at least twolayers of reinforcement elements, oriented substantiallycircumferentially, arranged axially on either side of the median planeof the tire in the lateral zones of said crown. These layers make itpossible to withstand the forces due to centrifugation at high speed.They are preferably arranged radially internally relative to the twolayers of circumferentially oriented reinforcement elements of theworking block. These two reinforcement layers have the advantage ofincreasing the wrapping of the lateral zones of the crown withoutincreasing the thickness thereof.

The crown reinforcement may further comprise at least two layers ofreinforcement elements, which are parallel to each other in each layerand crossed from one layer to the next, forming an angle α, of between5° and 35° with the circumferential direction for reinforcing the driftrigidity of the tire. The reinforcement elements are for examplereinforcement elements such as those described in patent application WO02/085646.

The crown reinforcement may also comprise, arranged radially externallyrelative to the working block, a protective crown layer. This protectivelayer preferably extends axially beyond the axial width of the layers ofreinforcement elements of circumferential orientation.

As mentioned above, the aircraft tire according to the invention isparticularly advantageous in constituting a mounted assembly with awheel of monobloc type, because the possible deformation of the beads ofthe tire makes it possible in particular to mount and demount the tireon/from such a wheel. Furthermore, these mounting and demountingoperations can be effected more simply and more quickly than for a wheelconsisting of several parts. This has economic advantages of differentorders in particular as far as the direct means of implementing and theworkforce and its necessary training are concerned, as statedpreviously.

The invention thus proposes a use of a tire such as has been describedabove in a mounted assembly for aircraft as described previously, therim of which is of monobloc type comprising a drop-centre functionality.

The invention also proposes a use of a tire in a mounted assembly foraircraft as described previously, the wheel of which is of monobloc typecomprising a drop-centre functionality, said tire comprising at leastany one of the characteristics of the tire according to the invention asdescribed previously.

The invention also proposes a use of a tire such as has just beendescribed in a mounted assembly for aircraft, the inflation pressure ofwhich is greater than 9 bar and the relative deflection of which isgreater than 30%, consisting of a wheel and the tire, said wheelcomprising a rim for receiving the tire and more specifically seatsreceiving the beads of said tire, said rim being of the type consistingof several parts.

The invention also proposes a use of a tire in a mounted assembly foraircraft, the inflation pressure of which is greater than 9 bar and therelative deflection of which is greater than 30%, consisting of a wheeland the tire, said wheel comprising a rim for receiving the tire andmore specifically seats receiving the beads of said tire, said rim beingof the type consisting of several parts, said tire comprising at leastany one of the characteristics of the tire according to the invention asdescribed previously.

The invention also proposes a mounted assembly for aircraft, theinflation pressure of which is greater than 9 bar and the relativedeflection of which is greater than 30%, consisting of a wheel and atire as described previously, comprising in particular beads, said wheelcomprising a rim for receiving the tire and more specifically seatsreceiving the beads of said tire, said rim being of the type consistingof several parts.

The tire according to the invention also has advantages with regard tothe mounting and demounting of the mounted assembly in the case of awheel consisting of several parts, because the flexibility of the beadsof the aircraft tire according to the invention will make it possible tofacilitate the placement of the tire during mounting by reducing therisks of degradation thereof.

Furthermore, the tire according to the invention makes it possible tofacilitate the operations of demounting such mounted assemblies. Theextreme conditions of use of these mounted assemblies result in a verystrong connection between the tire and the rim, which means that it isnecessary to exert great forces on said tire; these must be exerted veryhomogeneously on the periphery of the sidewall of the tire when thelatter has rigid beads at the risk of blocking the mounted assembly assoon as the bead becomes positioned at an angle relative to the rim ofthe wheel. In the case of the invention, this operation is simplifiedowing to the flexibility of the beads of the tire. The tools and thequalifications of the workforce can thus be less specialized in the caseof the invention.

Other advantageous details and characteristics of the invention willbecome apparent hereafter from the description of examples of embodimentof the invention with reference to FIGS. 1 to 7, which represent:

FIG. 1, a diagram of an axial section through a tire according to theinvention,

FIG. 2, a diagram of a section through a cable according to theinvention,

FIG. 3, a perspective view showing the arrangement of part of thereinforcing threads of the carcass reinforcement,

FIG. 4, a diagram of a bead according to a second embodiment of theinvention,

FIG. 5, a diagram of an axial section through a tire according to avariant embodiment of the invention shown in FIG. 1,

FIG. 6, a diagram of an axial section through a tire according toanother variant embodiment of the invention shown in FIG. 1,

FIGS. 7 a, 7 b, 7 c, the stages of mounting a tire on a rim to form amounted assembly according to the invention.

FIGS. 1 to 7 are not shown to scale in order to simplify understandingthereof.

The aircraft tire 1 shown diagrammatically in axial half-section in FIG.1 comprises a crown 2, two sidewalls 3 and two beads 4. A carcassreinforcement 5 extends from one bead 4 to the other and is formed oftwo circumferential alignments 6 and 7 of reinforcement elements. Thecircumferential alignments of the reinforcement elements 6 and 7 areoriented radially in the sidewalls 3 and are formed of reinforcementelements of aromatic polyamide or aramid. The reinforcement elements arearranged parallel to one another and are separated by a layer of mix 8the nature and the modulus of which are adapted according to theirposition in the tire.

Anchoring of the two circumferential alignments 6 and 7 is effected inthe beads 3 by alignments or “stacks” 9 of circumferentially orientedwound cables arranged axially on either side of each circumferentialalignment of the reinforcement elements 6 and 7. Each alignment or stack9 of circumferentially oriented cables may be obtained by helicalwinding of a cable. The radial reinforcement elements of the carcassreinforcement and the circumferentially oriented cables are separatedfrom each other by a bonding or anchoring rubber mix 10 in order toavoid any direct contact of one reinforcement element with another. Thisanchoring rubber mix according to the invention has a rigidity such thatits modulus of extension at 10% deformation is of between 10 and 20 MPa.The anchoring rubber mix according to the invention has as othermechanical properties excellent creep resistance at high temperature andvery good stability at high temperature. The rigidity selected impartsto the bead structures described sufficient flexibility to make itpossible to effect easily the mounting and demounting of the tireswithout adversely affecting the endurance performance; the creepresistance is essential to obtain solid and durable anchoring of thecarcass reinforcements in the beads and the thermal stability at hightemperature is also important owing to the very harsh thermal conditionsto which the tires may be subjected during operation.

The tension which develops in the radial reinforcement elements uponinflation of the tire 1 is taken up in particular by the lateraladhesion between each circumferential alignment 6 and 7 and the stacks 9of circumferentially oriented cables. This bead structure ensuresexcellent anchoring, which remains very effective even for the very highinflation pressures of aircraft tires, which are greater than 9 bar andpossibly attain 25 bar in certain specific applications. The tires haveexhibited an ability to resist four times the use pressure as requiredby standard TSO C62.

The stacks 9 of circumferentially oriented cables are distributed intothree groups, two stacks 11 arranged axially externally to the carcassreinforcement 5 on the outside of the tire, two stacks 13 arrangedaxially internally relative to the carcass reinforcement 5, on theinside of the tire and four stacks 12 arranged between the twocircumferential alignments 6 and 7 of the carcass reinforcement 5.

The invention may also provide for cones of rubber mixes to be placedaxially between the carcass reinforcement and the stacks 9 ofcircumferentially oriented cables to permit placement of thecircumferentially oriented cables such that the axial distance betweenthem and the carcass reinforcement increases in the radial direction.This variant embodiment is not illustrated in the figures. Suchplacement of the cables has been described in French application FR0209355.

In the case of the tire described, considering the number of turnsarranged internally and externally relative to the carcassreinforcement, then:ΣR _(I) /ΣR _(E)≅1.24.

This has the advantage of homogenizing the mechanical stress applied onthe circumferentially oriented cables in the bead.

It may also be noted that the number of turns of the stacks decreasesgradually with distance relative to the axis of rotation A of the tire1. The result is a substantially conical form of the arrangement of thecircumferentially oriented cables. This has the advantage of greatlystabilizing the beads 4 upon inflation of the tire and upon passage intothe contact area during operation.

All the turns of the stacks 9 are embedded in the rubber mix 10 of amodulus of extension at 10% deformation of between 10 and 20 MPa toensure good taking-up of the forces due to the inflation pressure andhence excellent anchoring of the carcass reinforcement in the beads 4.

FIG. 2 shows a cable 80 used, according to the invention, in acircumferential winding as anchoring means for the reinforcementelements of the carcass reinforcement. The cable 80 is a layered cableof formula 9.35, that is to say formed of 9 elementary wires of adiameter of 35/100 mm; the cable 80 satisfies the formula 2+7 with twowires 81, constituting the first layer, twisted together to form a pliedyarn, and seven wires 82, forming the outer layer, wound together in ahelix around the first layer. FIG. 2 illustrates this winding by showingthe seven wires 82 in contact with the circle 83 representing the spaceoccupied by the plied yarn formed of the two wires 81 of the firstlayer. The wires 81, 82 are made of steel having a carbon content ofbetween 0.7 and 0.9%. The wires have been treated beforehand so as tocomprise a brass coating which promotes adhesion of the wire to therubber. The wires have a work-hardening ratio of less than 3.5. Thecable has a total diameter D′, corresponding the diameter of the circle84 circumscribed on the outer layer, of 1.35 mm. The measurement of thepenetrability of this cable effected according to the method describedpreviously resulted in a value of 100%. The breaking load of the cableis equal to 198 daN and its elongation at break is 5.4%. The elongationat break is obtained after a heat treatment such as the one mentionedabove; the heat treatment makes it possible to increase the elastic andplastic elongations which are added to the structural elongation. Thelatter is equal to 0.1% for the cable 80 of formula 9.35.

Another layered cable, of formula 13.35, was tested; this cable isformed of 13 elementary wires of a diameter of 35/100 mm and of formula4+9, with 4 wires, constituting the first layer, twisted together toform a plied cable, and 9 wires, forming the outer layer, wound togetherin a helix around the first layer. The elementary wires are the same asin the previous case. The measurement of the penetrability of this cableeffected according to the method described previously resulted in avalue of 80%. The breaking load of the cable is equal to 282 daN and itselongation at break is 6.4%. It should be noted that the structuralelongation of this cable of formula 13.35 is 0.2%.

FIG. 3 is a perspective view of one of the circumferential alignments ofthe reinforcement elements, alignment 6, in which only the reinforcementelements are shown. In this FIG. 3, there can be seen thecircumferential alignment 6 of the reinforcement elements of the carcassreinforcement which is formed of portions of reinforcement elements 17.At their radially lower ends, the portions of reinforcement elements 17form juxtaposed loops 18, located in the bead 4. These loops 18 areadjacent and do not overlap. Axially on either side of thecircumferential alignment 6 of the reinforcement elements of the carcassreinforcement, are shown only the stacks 11 and 12, of circumferentiallyoriented reinforcement elements, directly adjacent to this alignment 6.For clarity of the drawing, only the circumferential alignment 6 ofreinforcement elements and two stacks have been shown, but thecircumferential alignment 7 of reinforcement elements of the carcassreinforcement has the same arrangement of the portions of reinforcingthreads 17.

FIG. 4 illustrates a bead 21 and a sidewall 22 of a second embodiment ofa tire 20 according to the invention in which the carcass reinforcement23 is formed of two circumferential alignments 24, 25 of reinforcementelements of aromatic polyamide or aramid. In the bead 21 there arearranged stacks 27 of cables of circumferential orientation. Thesestacks 27 are here separated into three groups. There are foundsuccessively axially from the inner side of the bead towards the outerside, two stacks 28 arranged internally relative to the circumferentialalignment of reinforcement elements of the carcass reinforcement 24,three stacks 29 arranged between the circumferential alignments ofreinforcement elements of the carcass reinforcement 24 and 25, and twostacks 30 arranged externally relative to the circumferential alignmentof reinforcement elements of the carcass reinforcement 25.

As previously, the number of turns of circumferentially oriented cablesis such that it is ensured that the total of the rigidities of extensionof the stacks arranged externally relative to the carcass reinforcementis substantially of the same order as the total of the rigidities ofextension of the stacks arranged internally relative to the carcassreinforcement 23.

The outer surface of the bead 21 comprises a seat 32, a frustoconicalwall of substantially radial orientation 33 adjacent radially internallyto a wall 34 the section of which is an arc of a circle EF of centre C.C is located to the outside of the bead 21. Considering the line CDwhich passes through the bead, forming an angle α=+45±5 degrees relativeto the axis of rotation A of the tire (this angle is determined when thetire is mounted on its rim), it will be noted that all thecircumferentially oriented reinforcement elements 27 are arranged at aradial distance from the axis A less than or equal to this line CD. Thisline CD defines substantially a very rigid embedding zone, in which thedeformations are very much reduced, and a zone of flexure radially aboveCD. The fact that all the circumferentially oriented reinforcementelements are in the embedding zone reinforces the endurance of the bead.

This outer surface of the bead is intended to come to bear against thewall of a rim 35 whose outer profile is also shown in FIG. 4. Thisprofile comprises the seat 36 and the substantially radial wall of thehook 37 followed by the flange 38. The flange 38 has a cross-section inthe shape of an arc of a circle of centre C′. The highest point ofdiameter is B, of radius R_(J). The point E arranged on the axiallyouter surface of the bead 21 is intended to come into contact withsubstantially the point B. When the tire is mounted on the rim 35, thesurfaces 34 and 38 are homocentric, that is to say that their centers Cand C′ are the same. The point E is located on a circumference ofdiameter Φ. We have the relationship:Φ=2(R _(J)−ε)where ε is between 0.5 and 2 mm.

This slight offset of the point E between its free position and itsposition mounted on the rim, in contact with B, enables the bead to beslightly extended when it is mounted on the rim and promotes the qualityof the contact obtained. This contact as far as point E reinforces thestability of the bead during the pressurization of the tire and duringpassage into the contact area during operation. Consequently, it will benoted that the circumferential alignments of the carcass reinforcementare substantially less stressed in compression upon passage into thecontact area, contrary to what happens for aircraft tires ofconventional structure.

FIG. 1 also shows a first example of a crown reinforcement 14. This isformed of a working block comprising two layers of reinforcementelements 15 and 16 of substantially circumferential orientation obtainedby helical winding of at least one reinforcement element. The number oflayers of reinforcing thread and the laying pitch are adapted accordingto the dimension of the tire and its conditions of use. This embodimentof a crown reinforcement has the advantage of providing very effectivewrapping which minimizes the variation in the dimensions of the tireupon inflation and at high speed. It will be noted that the change inthe profile may be three to four times less than for a conventionalaircraft tire such as a 30×8.8R15 AIRX. This excellent wrapping also hasthe advantage of not greatly extending the mixes forming the tread ofthe crown of the tire. The surface cracking of the tread due to theozone present in the air is greatly reduced.

The crown reinforcement 41 of the tire 40 shown in FIG. 5 comprises, aspreviously, two layers of reinforcement elements of substantiallycircumferential orientation 15 and 16, and is finished off by two layers42 and 43 of substantially circumferentially oriented reinforcementelements, arranged axially on either side of the median plane of thetire in the lateral zones of the crown. They make it possible toreinforce the wrapping of the lateral zones L of the crown. The layers42 and 43 are arranged radially between the layers 15 and 16 and thecarcass reinforcement 5.

The reinforcement 41 is also finished off by a protective crown layer 44arranged radially externally relative to the other layers of the crownreinforcement 41. This protective crown layer may be formed of metallicreinforcement elements which undulate so that they are not stressed innormal operation. It should be noted that this protective layer extendsaxially beyond the layers 15 and 16 on either side of the median plane Pof the tire by an axial distance a.

FIG. 6 shows a tire 50 with a crown reinforcement 51 furthermorecomprising two layers 52, 53 of reinforcement elements, which areparallel to each other in each layer and crossed from one layer to thenext, forming with the circumferential direction an angle α of between5° and 35°. These two layers are arranged radially below the layers ofcircumferential reinforcement elements 15 and 16. They increase thedrift thrust of the tire 30 relative to that of the tire 40.

FIGS. 7 a, 7 b, 7 c illustrate by sectional diagrams the stages ofmounting a tire according to the invention on a wheel 72 of monobloctype comprising a drop-centre functionality represented by theindentations 73. The figures show diagrammatically only the beads 70, 71of the tire according to the invention.

In FIG. 7 a, it will be observed that part of the first bead 70 ispassed over the rim flange 74 and is placed in the indented zone or dropcentre 73. It is then possible to pass the rest of the bead 70 over theflange 74 by slightly ovalising the corresponding bead of the tire. Thedeformation of the bead 70 necessary to carry out this step must make itpossible to obtain a diametrically opposed edge-to-edge distance of thebead 70 equivalent to the length V. This deformation of the bead isfurthermore accompanied by warping of the bead 70 making it possiblegradually to pass the bead 70 over the rim flange 74. The diameter ofthe bead 70 corresponds substantially to the diameter W of the rim seatwhich is to receive the bead.

FIG. 7 b shows that the same applies for passing the second bead 71 overthe flange 74 of the rim 72. Part of the first bead 71 is passed overthe rim flange 74 and is placed in the indented zone or drop centre 73.As previously for the bead 70, it is then possible to pass the rest ofthe bead 71 over the flange 74 by slightly ovalising the correspondingbead of the tire, accompanied by warping thereof.

FIG. 7 c illustrates the end of mounting by a step of inflation to apressure such as will ensure that the beads 70, 71 are placed properlyon the seats 75, 76 bearing on the rim flanges.

Experiments relating to the anchoring rubber mix have shown that inorder to obtain good endurance results, an anchoring rubber mixcontaining an “SBR” synthetic elastomer, or butadiene/styrene copolymer,of a Tg of between −70° and −30° C., used alone or in a blend with “BR”,or polybutadiene, can be used. Preferably, the BR has a Tg of between−110° and −90° C. The synthetic elastomer(s) is/are used in a totalproportion of at least 50% of the total weight of elastomer, the balancebeing formed by natural rubber (“NR”). The anchoring rubber mixadditionally contains reinforcing fillers such as carbon black and avulcanization system appropriate for obtaining the desired rigidity. Thecircumferential reinforcement elements, in the examples shown, arebrass-coated metal cables. It is therefore necessary for the anchoringrubber mix to have a high sulphur content and to contain additivespromoting adhesion to the brass (for example cobalt or nickel metalsalts). For example, an amount of sulphur of between 5 and 8% of thetotal weight of elastomer and an amount of carbon black of between 60and 70% of the total weight of elastomer are used. Carbon black N347 maybe preferably used.

Four mixes were produced and tested to illustrate the characteristics ofthe anchoring rubber mixes according to the invention.

The main characteristics of the formulation of these mixes are found inthe table below. Products 1 2 3 4 NR 100 80 40 40 SBR2300 0 10 30 60BR113 0 10 30 0 N347 62 62 62 62 Sulphur 7 7 7 7These four mixes were tested thus:

-   -   rigidity: determination of the elasticity modulus at 10%        extension and ambient temperature,    -   creep: static creep test at 150° C. for 5 hours as described        previously, and

thermal stability: rheometry test at 197° C. for 10 min as describedpreviously. Test 1 2 3 4 Elasticity 10.6 11.8 11.6 13.0 modulus Creeptest Break after Break after 60 OK OK 30 min min τ — — 1 × 10⁻³/min 0.6× 10⁻³/min r 35% 26% 1.5% 7.7%The four mixes have satisfactory rigidity.

The mix 1, based solely on natural rubber, has a static creep resistanceat high temperature which is completely inadequate. Breaking of the testpieces was observed after 30 minutes' testing. Its thermal stability isalso not satisfactory, since the mix has a very marked amount ofreversion.

Mix 2 has improved results compared with the first, but is notsatisfactory either.

Mixes 3 and 4 successfully pass the static creep and rheometry tests.Their creep resistance is entirely correct, and their thermal stabilityat high temperature is, too. Mix 3, which comprises three elastomers,has a slightly more satisfactory reversion result than mix 4.

Tire tests were also carried out with anchoring rubber mixes offormulations similar to the mixes 1 to 4 of the test.

A tire of dimension 30×8.8 R 15/16/225 was tested which comprised:

-   -   as carcass reinforcement two circumferential alignments of        reinforcement elements;    -   as circumferentially oriented cables steel cables such as those        described in FIG. 2, of formula 9.35, and distributed in 7        stacks 27 (as illustrated in FIG. 4):        -   2 axially innermost stacks with 12 and 15 turns,        -   3 stacks between the circumferential alignments 24 and 25            with 17, 14 and 16 turns,        -   2 axially outermost stacks with 11 and 7 turns.    -   a crown reinforcement with two layers of reinforcement elements        oriented substantially circumferentially formed of plied cables.

The tires exhibited a correct aptitude for the mounting and demountingoperations, but only those comprising an anchoring rubber mixcorresponding to the formulations of mixes 3 and 4 exhibited sufficientendurance of the anchoring of the carcass ply in the beads.

Furthermore, the tires corresponding to mixes 3 and 4 underwentbursting-resistance tests and the maximum pressures measured were of theorder of 58 bar. They are also characterized by an amount of elongationof their development between zero pressure and their operating pressureof 15 bar of the order of 1.5%. These tires also successfully underwenttakeoff tests similar to the standardized tests for certification ofaircraft tires.

The building of such a tire according to the invention mayadvantageously be effected on a rigid core which imposes the form of itsinner cavity, such as those described by EP 242 840 or EP 822 047, whichare incorporated in the present application by reference. There areapplied to this core, in the order required by the final architecture,all the constituents of the tire, which are arranged directly in theirfinal position, without undergoing shaping at any moment of the buildingoperation. The curing takes place on the core, the latter being removedonly after the vulcanization phase has finished.

This method of manufacture has the advantage of greatly reducing, oreven eliminating, the pre-stresses imposed on the reinforcing threads,particularly those oriented at 0°, during the traditional shapingphases.

The casing may also be partially cooled on the core in order to keep thereinforcement elements in the state of deformation imposed duringlaying.

Equivalently, it is also possible to manufacture the tire on a drum suchas described in WO 97/47 463 or EP 0 718 090, provided that the blank ofthe tire is shaped before laying the circumferentially oriented cables.

The circumferentially oriented cables may also be laid on a form havinga geometry identical to the form intended in the curing mould. The crownblock is then assembled with the complementary blank of the tire usingtransfer techniques known to the person skilled in the art, then, stillusing known principles, the tire is fitted and pressurized by deployinga membrane inside the tire.

This embodiment also guarantees the absence of pre-stresses due to theshaping in the vulcanization press.

Whatever the manufacturing method selected for producing a tireaccording to the invention in which the anchoring means for thereinforcement elements of the carcass reinforcement within each bead arecircumferentially oriented cables axially bordering the circumferentialalignments of said reinforcement elements of the carcass reinforcement,it would appear that the combination of the cables laid in acircumferential orientation and the anchoring rubber mix according tothe invention makes it possible to produce tires which may be mounted onrims of wheels of monobloc type.

Furthermore, the selection of the cables laid in a circumferentialorientation in the zone of the bead to anchor the reinforcement elementsof the carcass reinforcement makes it possible to obtain satisfactorymanufacturing yields, because the selection of these cables permitshooking during their laying in the uncured state which is sufficient forthem not to risk becoming detached or simply displaced before the curingphase.

The description of the figures has been limited to the case of tires inwhich the anchoring means for the reinforcement elements of the carcassreinforcement within each bead are circumferentially oriented cablesaxially bordering the circumferential alignments of said reinforcementelements of the carcass reinforcement but, as previously mentioned, itis also directed at tires in which the carcass reinforcement comprisesat least one layer of reinforcement elements having a zone of upturnaround at least one circumferentially oriented reinforcement elementsuch as a bead wire.

The invention must also not be understood as being limited to the caseof mounted assemblies formed in particular of a wheel of monobloc typecomprising a drop-centre functionality; as explained previously, theinvention is also directed at mounted assemblies formed of a tireaccording to the invention and a conventional wheel for aircraftapplications which is formed of several parts.

1. A mounted assembly for aircraft formed of a wheel and a tirecomprising in particular beads, the inflation pressure of which isgreater than 9 bar and the relative deflection of which is greater than30%, said wheel comprising a rim for receiving the tire and morespecifically seats receiving the beads of said tire, and said rimcomprising a drop-centre functionality.
 2. A mounted assembly foraircraft according to claim 1, wherein the rim is of monobloc type.
 3. Amounted assembly for aircraft according to claim 1, wherein the seats ofthe rim have a slope greater than 5° and preferably less than 15°.
 4. Amounted assembly for aircraft according to claim 1, wherein the beads ofthe tire are ovalisable.
 5. A mounted assembly for aircraft according toclaim 1, wherein the beads of the tire may be warped.
 6. A mountedassembly for aircraft according to claim 1, the tire comprising a crown,two sidewalls and two beads, a carcass reinforcement anchored in the twobeads and a crown reinforcement, in which the carcass reinforcementcomprises at least one circumferential alignment of reinforcementelements and in which the means for anchoring said reinforcementelements within each bead comprise at least one circumferentiallyoriented reinforcement element, the carcass reinforcement of the tirecomprising at least one layer of reinforcement elements having a zone ofupturn around at least one circumferentially oriented reinforcementelement
 7. A mounted assembly for aircraft according to claim 6, whereinthe circumferentially oriented reinforcement element is a bead wire. 8.A mounted assembly for aircraft according to claim 1, comprising acrown, two sidewalls and two beads, a carcass reinforcement anchored inthe two beads and a crown reinforcement, in which the carcassreinforcement comprises at least one circumferential alignment ofreinforcement elements and in which the means for anchoring saidreinforcement elements within each bead comprise at least onecircumferentially oriented reinforcement element, the means foranchoring said reinforcement elements within each bead of the tirecomprising circumferentially oriented reinforcement elements axiallybordering said circumferential alignments of said reinforcement elementsof the carcass reinforcement.
 9. A mounted assembly for aircraftaccording to claim 8, wherein the circumferentially orientedreinforcement elements are cables.
 10. A mounted assembly for aircraftaccording to claim 1, the tire comprising in particular a carcassreinforcement, wherein the reinforcement elements of the carcassstructure of the tire are arranged in a radial orientation.
 11. Anaircraft wheel comprising a rim for receiving a tire, comprising inparticular beads, and more specifically seats receiving the beads ofsaid tire, the inflation pressure of the mounted assembly formed of thewheel and said tire being greater than 9 bar and the relative deflectionof which is greater than 30%, wherein said rim comprises a drop-centrefunctionality.
 12. An aircraft wheel according to claim 11, wherein therim is of monobloc type.
 13. An aircraft wheel according to claim 11,wherein the seats of the rim have a slope greater than 5°, andpreferably less than 15°.
 14. An aircraft tire, the inflation pressureof which is greater than 9 bar and the relative deflection of which isgreater than 30%, comprising a crown, two sidewalls and two beads, acarcass reinforcement anchored in the two beads and a crownreinforcement, in which the carcass reinforcement comprises at least onecircumferential alignment of reinforcement elements and in which themeans for anchoring said reinforcement elements within each beadcomprise at least one circumferentially oriented reinforcement element,and at least one anchoring rubber mix in contact with thecircumferential reinforcing thread and the reinforcement elements of thecarcass reinforcement, the beads of the tire being ovalisable.
 15. Atire according to claim 14, wherein the beads of the tire can be warped.16. An aircraft tire, the inflation pressure of which is greater than 9bar and the relative deflection of which is greater than 30%, comprisinga crown, two sidewalls and two beads, a carcass reinforcement anchoredin the two beads and a crown reinforcement, in which the carcassreinforcement comprises at least one circumferential alignment ofreinforcement elements and in which the means for anchoring saidreinforcement elements within each bead comprise at least onecircumferentially oriented reinforcement element, and at least oneanchoring rubber mix in contact with the circumferential reinforcingthread and the reinforcement elements of the carcass reinforcement, saidanchoring rubber mix having an elasticity modulus at a deformation of10% of less than 20 MPa.
 17. A tire according to claim 16, wherein theanchoring rubber mix comprises at least one synthetic elastomer includedin the group of SBRs and BRs with a total proportion of syntheticelastomer greater than 50% of the total weight of elastomers.
 18. A tireaccording to claim 16, wherein the anchoring rubber mix comprises an SBRof a Tg of between −70° and −25° C. with a proportion by weight greaterthan 20% of the total weight of elastomers.
 19. A tire according toclaim 16, wherein the anchoring rubber mix comprises a BR of a Tg ofbetween −110° and −90° C. with a proportion by weight less than 40% ofthe total weight of elastomers.
 20. A tire according to claim 16,wherein the anchoring rubber mix withstands without breaking a staticcreep stress at 150° C. under an initial stress of 2.35 MPa for at leastfive hours.
 21. A tire according to claim 20, wherein the anchoringrubber mix has an amount of static creep at 150° C. under an initialstress of 2.35 MPa of less than 2×10⁻³ mm⁻¹ for between three and fivehours.
 22. A tire according to claim 16, wherein the anchoring rubbermix has an amount of reversion after 10 min at 197° C. of less than 10%and preferably of less than 5%.
 23. A tire according to claim 14 or 16,wherein the carcass reinforcement comprises at least one layer ofreinforcement elements having a zone of upturn around at least onecircumferentially oriented reinforcement element.
 24. A tire accordingto claim 23, wherein the circumferentially oriented reinforcementelement is a bead wire.
 25. A tire according to claim 14 or 16, whereinthe means for anchoring said reinforcement elements within each beadcomprise circumferentially oriented reinforcement elements axiallybordering said circumferential alignments of said reinforcement elementsof the carcass reinforcement.
 26. A tire according to claim 25, whereinthe circumferentially oriented reinforcement element are cables.
 27. Atire according to claim 26, wherein said cables have a penetrability ofbetween 80 and 100%, wherein the breaking load of the cables is greaterthan 150 daN and wherein said cables have an elongation at break greaterthan 4%.
 28. A tire according to claim 26, wherein the breaking load ofthe circumferentially oriented cables is less than 400 daN.
 29. A tireaccording to claim 26, wherein the elongation at break of thecircumferentially oriented cables is less than 8%.
 30. A tire accordingto claim 26, wherein said circumferentially oriented cables of saidanchoring means are formed of cords selected from among the groupconsisting of carbon, tungsten, aramid, glass-fiber or steel reinforcingthreads.
 31. A tire according to claim 26, the circumferentiallyoriented cables being metal ones, wherein said circumferentiallyoriented cables are heat-treated.
 32. A tire according to claim 26,wherein the surface of the circumferentially oriented cables comprisesan adherent coating, such as a brass coating.
 33. A tire according toclaim 14 or 16, wherein the reinforcement elements of the carcassstructure are arranged in a radial orientation.
 34. A tire according toclaim 25, in which, considering ΣR_(I) as being the total of therigidities of extension of the second reinforcing threads arrangedaxially internally relative to the carcass reinforcement, andconsidering ΣR_(E) as being the total of the rigidities of extension ofthe second reinforcing threads arranged axially on either side of thecarcass reinforcement: $0.6 \leq \frac{\sum R_{I}}{\sum R_{E}} \leq 1.5$35. A tire according to claim 34, in which:$0.7 \leq \frac{\sum R_{I}}{\sum R_{E}} \leq {1.3.}$
 36. A tireaccording to claim 14 or 16, in which, the outer surface of the beadscomprising a seat, a frustoconical wall of substantially radialorientation adjacent radially internally to a wall the section of whichis an arc of a circle EF of centre C, and considering a line CD passingthrough the bead, forming an angle α=+45±5 degrees relative to the axisA of the tire, all the second reinforcing threads are arranged at aradial distance from the axis A less than or equal to said line CD. 37.A tire according to claim 14 or 16, in which, said bead having an outersurface intended to come into contact with the corresponding surface ofthe seat and of the hook of said rim, after mounting on said rim andinflation of said tire, the contact zone between said outer surface ofsaid bead and said rim extends at least as far as point B of the hook ofmaximum radius R_(J).
 38. A tire according to claim 37, in which, Φbeing the diameter of the circumference of the outer surface of the beadintended to come to bear against the circumference of the hook of therim of maximum radius R_(J):Φ=2(R _(J)−ε) with ε being between 0.5 and 2 mm.
 39. A tire according toclaim 14 or 16, in which said first reinforcing threads of the carcassreinforcement form forward and return paths arranged adjacently, with,at the level of each bead, loops connecting one forward path to onereturn path each time.
 40. A tire according to claim 14 or 16, in whichsaid crown reinforcement comprises at least one working block with atleast two layers of reinforcing threads which are parallel in eachlayer, oriented substantially circumferentially and of high elasticitymodulus.
 41. A tire according to claim 40, in which, said crowncomprising a central zone and two lateral zones, said working blockfurthermore comprises two layers of reinforcement elements of highelasticity modulus, oriented substantially circumferentially, arrangedaxially on either side of the median plane of the tire in the lateralzones of said crown.
 42. A tire according to claim 41, in which said twolayers of reinforcement elements of high elasticity modulus of saidworking block are arranged radially to the inside of said two layers ofcircumferentially oriented reinforcing threads of said working block.43. A tire according to claim 40, in which said working block furthercomprises two layers of reinforcing threads, which are parallel to eachother in each layer and crossed from one layer to the next, forming anangle α, of between 5° and 35°, with the circumferential direction, saidreinforcing threads having a high elasticity modulus.
 44. A tireaccording to claim 40, in which said crown reinforcement furthermorecomprises, arranged radially externally relative to said working block,a protective layer extending axially beyond the axial width of saidlayer or layers of reinforcing threads of high elasticity modulus.